Generally, a belt power transmission mechanism configured to wind a belt on a plurality of pulleys has specifications where high tension is applied to the belt by making a circumferential length of the belt shorter than a circumferential length of a layout between the pulleys that are mounting targets for surely transmitting power between the pulleys.
In the case where such a belt power transmission mechanism described above has no tension pulley or the like capable of adjusting a shaft center position of the pulley, when a belt with the circumferential length shorter than the circumferential length of the layout between the plurality of pulleys is attached to the plurality of pulleys with all distances between mutual shafts fixed, one pulley is left lastly and the belt is previously wound on the other pulleys and tension is applied to the belt wound on the other pulleys, and a belt attachment tool for attaching the belt to outer peripheral surfaces of the pulleys while rotating the lastly left pulley is used.
For example, Patent Document 1 discloses a belt attachment tool used in the case of winding a belt on three pulleys. In a layout (see FIG. 2 etc. of Patent Document 1) of the three pulleys P1, P2 and P3, the belt attachment tool is mounted to the pulley P1 with the largest diameter and a long wound belt portion, and tension is applied to the belt V wound on the pulleys P2 and P3 other than the pulley P1, and the pulley P1 is rotated to thereby attach the belt to the three pulleys by using the belt attachment tool. Thus, in the case of attaching a belt to a plurality of pulleys by using the belt attachment tool, the pulley P1 with the largest diameter and a long wound belt portion tends to be selected as the pulley to which the belt attachment tool is mounted for a reason that “it is easier to attach a belt by lastly winding the belt on the pulley with a longer wound belt portion (it is easier to do winding work)”.
However, for reasons that “it may be preferable in some cases to first wind a belt on the pulley with the largest diameter and a long wound belt portion since a misalignment is increased when the belt is lastly wound on the pulley with the largest diameter and a long wound belt portion”, or “a component causing a barrier is present in the vicinity of the pulley with the largest diameter and a long wound belt portion and it may be physically difficult to do attaching work”, there are cases where the pulley with the largest diameter and a long wound belt portion cannot be selected as the pulley to which the belt attachment tool is mounted.
In such cases, a pulley (a pulley with a diameter smaller than that of the large-diameter pulley: hereinafter called a small-diameter pulley) other than the pulley with the largest diameter (hereinafter called a large-diameter pulley) has to be selected as the pulley to which a belt attachment tool is mounted.